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<h1>Penlight</h1>

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  <li><a href="https://github.com/lunarmodules/Penlight">GitHub Project</a></li>
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<h2>Contents</h2>
<ul>
<li><a href="#Functions">Functions</a></li>
<li><a href="#Fields">Fields</a></li>
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<h2>Libraries</h2>
<ul class="nowrap">
  <li><a href="../libraries/pl.html">pl</a></li>
  <li><a href="../libraries/pl.app.html">pl.app</a></li>
  <li><a href="../libraries/pl.array2d.html">pl.array2d</a></li>
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  <li><a href="../libraries/pl.import_into.html">pl.import_into</a></li>
  <li><a href="../libraries/pl.input.html">pl.input</a></li>
  <li><strong>pl.lapp</strong></li>
  <li><a href="../libraries/pl.lexer.html">pl.lexer</a></li>
  <li><a href="../libraries/pl.luabalanced.html">pl.luabalanced</a></li>
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  <li><a href="../libraries/pl.seq.html">pl.seq</a></li>
  <li><a href="../libraries/pl.sip.html">pl.sip</a></li>
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  <li><a href="../libraries/pl.xml.html">pl.xml</a></li>
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<h2>Classes</h2>
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  <li><a href="../classes/pl.Date.html">pl.Date</a></li>
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  <li><a href="../classes/pl.Set.html">pl.Set</a></li>
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<h2>Manual</h2>
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  <li><a href="../manual/01-introduction.md.html">Introduction</a></li>
  <li><a href="../manual/02-arrays.md.html">Tables and Arrays</a></li>
  <li><a href="../manual/03-strings.md.html">Strings. Higher-level operations on strings.</a></li>
  <li><a href="../manual/04-paths.md.html">Paths and Directories</a></li>
  <li><a href="../manual/05-dates.md.html">Date and Time</a></li>
  <li><a href="../manual/06-data.md.html">Data</a></li>
  <li><a href="../manual/07-functional.md.html">Functional Programming</a></li>
  <li><a href="../manual/08-additional.md.html">Additional Libraries</a></li>
  <li><a href="../manual/09-discussion.md.html">Technical Choices</a></li>
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<h2>Examples</h2>
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  <li><a href="../examples/seesubst.lua.html">seesubst.lua</a></li>
  <li><a href="../examples/sipscan.lua.html">sipscan.lua</a></li>
  <li><a href="../examples/symbols.lua.html">symbols.lua</a></li>
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  <li><a href="../examples/testconfig.lua.html">testconfig.lua</a></li>
  <li><a href="../examples/testglobal.lua.html">testglobal.lua</a></li>
  <li><a href="../examples/testinputfields.lua.html">testinputfields.lua</a></li>
  <li><a href="../examples/testinputfields2.lua.html">testinputfields2.lua</a></li>
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  <li><a href="../examples/which.lua.html">which.lua</a></li>
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<h1>Module <code>pl.lapp</code></h1>
<p>Simple command-line parsing using human-readable specification.</p>
<p> Supports GNU-style parameters.</p>


<pre>
lapp = <span class="global">require</span> <span class="string">'pl.lapp'</span>
<span class="keyword">local</span> args = lapp <span class="string">[[
Does some calculations
  -o,--offset (default 0.0)  Offset to add to scaled number
  -s,--scale  (number)  Scaling factor
  &lt;number&gt; (number) Number to be scaled
]]</span>

<span class="global">print</span>(args.offset + args.scale * args.number)
</pre>

<p> Lines beginning with <code>&apos;-&apos;</code> are flags; there may be a short and a long name;
 lines beginning with <code>&apos;&lt;var&gt;&apos;</code> are arguments.  Anything in parens after
 the flag/argument is either a default, a type name or a range constraint.</p>

<p> See <a href="../manual/08-additional.md.html#Command_line_Programs_with_Lapp">the Guide</a></p>

<p> Dependencies: <a href="../libraries/pl.sip.html#">pl.sip</a></p>


<h2><a href="#Functions">Functions</a></h2>
<table class="function_list">
	<tr>
	<td class="name" nowrap><a href="#quit">quit (msg, no_usage)</a></td>
	<td class="summary">quit this script immediately.</td>
	</tr>
	<tr>
	<td class="name" nowrap><a href="#error">error (msg, no_usage)</a></td>
	<td class="summary">print an error to stderr and quit.</td>
	</tr>
	<tr>
	<td class="name" nowrap><a href="#open">open (file[, opt])</a></td>
	<td class="summary">open a file.</td>
	</tr>
	<tr>
	<td class="name" nowrap><a href="#assert">assert (condn, msg)</a></td>
	<td class="summary">quit if the condition is false.</td>
	</tr>
	<tr>
	<td class="name" nowrap><a href="#add_type">add_type (name, converter[, constraint])</a></td>
	<td class="summary">add a new type to Lapp.</td>
	</tr>
	<tr>
	<td class="name" nowrap><a href="#process_options_string">process_options_string (str, args)</a></td>
	<td class="summary">process a Lapp options string.</td>
	</tr>
</table>
<h2><a href="#Fields">Fields</a></h2>
<table class="function_list">
	<tr>
	<td class="name" nowrap><a href="#show_usage_error">show_usage_error</a></td>
	<td class="summary">controls whether to dump usage on error.</td>
	</tr>
</table>

<br/>
<br/>


    <h2 class="section-header "><a name="Functions"></a>Functions</h2>

    <dl class="function">
    <dt>
    <a name = "quit"></a>
    <strong>quit (msg, no_usage)</strong>
    </dt>
    <dd>
    quit this script immediately.


    <h3>Parameters:</h3>
    <ul>
        <li><span class="parameter">msg</span>
            <span class="types"><a class="type" href="https://www.lua.org/manual/5.1/manual.html#5.4">string</a></span>
         optional message
        </li>
        <li><span class="parameter">no_usage</span>
            <span class="types"><span class="type">bool</span></span>
         suppress 'usage' display
        </li>
    </ul>





</dd>
    <dt>
    <a name = "error"></a>
    <strong>error (msg, no_usage)</strong>
    </dt>
    <dd>
    print an error to stderr and quit.


    <h3>Parameters:</h3>
    <ul>
        <li><span class="parameter">msg</span>
            <span class="types"><a class="type" href="https://www.lua.org/manual/5.1/manual.html#5.4">string</a></span>
         a message
        </li>
        <li><span class="parameter">no_usage</span>
            <span class="types"><span class="type">bool</span></span>
         suppress 'usage' display
        </li>
    </ul>





</dd>
    <dt>
    <a name = "open"></a>
    <strong>open (file[, opt])</strong>
    </dt>
    <dd>
    open a file.
 This will quit on error, and keep a list of file objects for later cleanup.


    <h3>Parameters:</h3>
    <ul>
        <li><span class="parameter">file</span>
            <span class="types"><a class="type" href="https://www.lua.org/manual/5.1/manual.html#5.4">string</a></span>
         filename
        </li>
        <li><span class="parameter">opt</span>
            <span class="types"><a class="type" href="https://www.lua.org/manual/5.1/manual.html#5.4">string</a></span>
         same as second parameter of <a href="https://www.lua.org/manual/5.1/manual.html#pdf-io.open">io.open</a>
         (<em>optional</em>)
        </li>
    </ul>





</dd>
    <dt>
    <a name = "assert"></a>
    <strong>assert (condn, msg)</strong>
    </dt>
    <dd>
    quit if the condition is false.


    <h3>Parameters:</h3>
    <ul>
        <li><span class="parameter">condn</span>
            <span class="types"><span class="type">bool</span></span>
         a condition
        </li>
        <li><span class="parameter">msg</span>
            <span class="types"><a class="type" href="https://www.lua.org/manual/5.1/manual.html#5.4">string</a></span>
         message text
        </li>
    </ul>





</dd>
    <dt>
    <a name = "add_type"></a>
    <strong>add_type (name, converter[, constraint])</strong>
    </dt>
    <dd>
    add a new type to Lapp.  These appear in parens after the value like
 a range constraint, e.g. '<ival> (integer) Process PID'


    <h3>Parameters:</h3>
    <ul>
        <li><span class="parameter">name</span>
            <span class="types"><a class="type" href="https://www.lua.org/manual/5.1/manual.html#5.4">string</a></span>
         name of type
        </li>
        <li><span class="parameter">converter</span>
         either a function to convert values, or a Lua type name.
        </li>
        <li><span class="parameter">constraint</span>
            <span class="types"><span class="type">func</span></span>
         optional function to verify values, should use lapp.error
 if failed.
         (<em>optional</em>)
        </li>
    </ul>





</dd>
    <dt>
    <a name = "process_options_string"></a>
    <strong>process_options_string (str, args)</strong>
    </dt>
    <dd>
    process a Lapp options string.
 Usually called as <code>lapp()</code>.


    <h3>Parameters:</h3>
    <ul>
        <li><span class="parameter">str</span>
            <span class="types"><a class="type" href="https://www.lua.org/manual/5.1/manual.html#5.4">string</a></span>
         the options text
        </li>
        <li><span class="parameter">args</span>
            <span class="types"><a class="type" href="https://www.lua.org/manual/5.1/manual.html#5.4">{string}</a></span>
         a table of arguments (default is <code>_G.arg</code>)
        </li>
    </ul>

    <h3>Returns:</h3>
    <ol>

        a table with parameter-value pairs
    </ol>




</dd>
</dl>
    <h2 class="section-header "><a name="Fields"></a>Fields</h2>

    <dl class="function">
    <dt>
    <a name = "show_usage_error"></a>
    <strong>show_usage_error</strong>
    </dt>
    <dd>
    controls whether to dump usage on error.
 Defaults to true







</dd>
</dl>


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